Invasion of the New-Zealand wheat bug Nysius huttoni in the Netherlands (Heteroptera:Lygaeidae)In 2006 the European Invertebrate Survey - Netherlands, by order of the National PlantProtection Organisation, conducted a survey of the distribution and population characteristicsof the true bug Nysius huttoni White, 1878. This is originally an endemic species of NewZealand, which was first discovered in the Netherlands in 2002 (Aukema et al. 2005).Presumably this species has been introduced to Europe through the harbour of Antwerp. InNew Zealand this species is an economically important pest species, known as the wheat bug(Schaefer & Panizzi 2000). They feed on the seeds of wheat and enzymes in the saliva degradethe gluten giving rise to runny dough that is unsuitable for baking (Schaefer & Panizzi 2000).The goal of the survey conducted in the Netherlands, and partially in Belgium, was to revealthe distribution, the population characteristics such as the phenology and the frequency of thedifferent wing morphs within the populations, and the possible damage to crops.A survey of potential sites was carried out, as well as a standardised monitoring of, first two, andlater three, populations.Nysius huttoni occurs throughout the south-western part of the Netherlands (fig. 8, 9),suggesting that the adults are capable of flying over large waterways like the Westerscheldeand the Oosterschelde. Nysius can be found on all kinds of waste grounds, even of the smallestsize. The only condition is the presence of acrocarpous mosses. The animals do not feed onthese mosses, but merely use them as a shelter and as a place to hibernate.During the entire survey period (from April 14 - October 26) adults of Nysius huttoni could beobserved in the field. However, the nymphs were first found on April 25. Therefore, in theNetherlands this species apparently hibernates as an adult, as it does in New Zealand. Duringthe monitoring of the populations there were two periods, June 2 - July 31 and September 1 -October 11, in which teneral specimens were found. These are specimens that recently moultedto adult. These two periods, combined with the fact that this species hibernates as an adult,indicates that there are at least two generations per year, presumably more.On average 25% of the individuals of the monitored populations were macropterous.Macropterous individuals have fully developed wings and flight muscles. They can contribute todispersal over longer distances. There were significantly more macropterous individuals amongthe females (31.8%) than among the males (20.3%) (p = 0.0001). There were no significantdifferences between the three populations.No damage to crops could be established. Not one specimen was found inside a crop field, noramong the crops. Besides, no damage to other vegetation could be established at places whereN. huttoni was present. Even after a long period of drought no damage could be established.Nysius huttoni is a recent introduction into Belgium and the Netherlands, not known prior to2002. There are still numerous places with suitable habitat. Waterways pose no barrier for thespread of N. huttoni. Around 25% of the population is macropterous and thus capable of longdistance dispersal. Therefore it is expected that this species may spread over the major part ofthe Netherlands, and probably other parts of north-western Europe.